1. Field of the Invention
The present invention relates to image sensing modules, and particularly to an image sensing module capable of actively switching sense image capture frequency.
2. Description of the Prior Art
Generally speaking, image sensors are utilized for sensing light to generate sense images. Image sensors can be applied to many fields, including optical touch devices, optical distance measurement devices, or optical image capture devices. An optical touch device can determine whether or not the image sensor senses an object (such as a user's finger) according to sense images generated by the image sensor. When the image sensor captures sense images at a relatively high frequency, the optical touch device may more rapidly determine whether or not the image sensor senses the object. Thus, the image sensor uses a relatively higher frequency to capture the sense images to allow the optical touch device to respond rapidly to user controls, so as to provide real time detection of objects (such as user fingers).
In the prior art, the image sensor always operates at the same frequency, regardless of whether or not an object is detected. In other words, even if the image sensor has detected an object, the image sensor will continue to capture images at the same high frequency to keep detecting the object's position. However, the object detected by the image sensor typically does not move rapidly. For example, when a user operates an optical touch device, his/her fingers do not move quickly. In other words, the image sensor could actually use a low frequency to capture images, and would still be able to detect the object's position. Thus, the prior art image sensor wastes power by capturing images at the high frequency after detecting the object.